1. Technical Field
The invention relates to a roller for thermally treating web-shaped media, comprising a roller body which is rotatable about its central longitudinal axis and peripheral bores introduced in axial parallel in the roller body, for conveying a liquid heating medium.
2. Description of the Related Art
Such a roller is known for example from DE 40 36 121 A1 and is to be described in the following by referring to FIG. 3 which shows a partial, longitudinal section through such a roller.
In FIG. 3, a heating and/or cooling roller for working material webs, such as for example paper, is indicated as a whole by the reference numeral 8. The roller 8 comprises a roller body 10, on whose two end faces flange trunnions 30a, 30b are mounted using attaching means 13, i.e. bolts or screws. In this way, the flange trunnion 30a serves both to bear the roller in a roller bearing (not shown) and to charge/discharge the roller 8 with/of liquid heating/cooling medium, which is firstly guided via a supply line 16 through the flange 30a into the interior of the roller 8 and is then directed via the line 16a and other connecting lines into axially parallel, peripheral bores 20. The peripheral bores 20 are connected to each other by lines in such a way that a series flow arrangement of peripheral bores is realized. Used heating/cooling liquid can be removed via an internal space 12 of the roller via a line 14a. 
At the peripheral bore 20 in question, a line 19 is provided at the opposite end of the roller 8, said line 19 removing the used liquid from the roller 8 via other lines, via the thermally insulated line 14a and a discharge line 14. The flange trunnion 30b is usually connected to a drive for rotationally moving the roller 8.
If such rollers are relatively short, in combination with a large diameter, then they can be regarded as xe2x80x9crigid rotorsxe2x80x9d which can be balanced by mounting balancing weights in two planes, i.e. at the ends of the roller.
Unlike such xe2x80x9crigid rotorsxe2x80x9d, long and slender rollers for treating web-shaped media at high speeds with respect to their dynamic running characteristics have to be regarded as xe2x80x9celastic rotorsxe2x80x9d. In these elastic rotors, mounting balancing weights in two planes, i.e. at the ends of the roller, is no longer sufficient, i.e. satisfactory running characteristics are only achieved if the mass distribution can be specifically influenced in another plane near the center of the roller.
Various possibilities for such xe2x80x9ctri-planar balancingxe2x80x9d have already been made known. FIG. 1 of DE 33 04 076 A1, for instance, proposes a roller comprising a shrunk-in displacement body, in which balancing weights are mounted in the center of the roller, on said displacement body.
In the case of deflecting rollers made of thin steel lines, devices can be attached in the center of the central bore, and balancing weights in turn mounted on said devices.
However, all these measures make it necessaryxe2x80x94once it has been established that a correction is required in the center of the roller, for example when checking a roller on a balancing machinexe2x80x94firstly to dismantle the roller and in particular to remove the screwed-on trunnions on the two ends of the roller body, so that the correction weights can be mounted in the roller.
In addition, FIG. 3 in DE 33 04 076 A1 proposes mounting containers in the interior of the roller which can be filled from outside with different quantities of liquid. This would then theoretically enable a correction in the third balancing plane without having to dismantle the roller. However, this theoretical possibility has never been put into practice.
The invention is based on the object of providing a roller for thermally treating web-shaped media of the type cited, in which the disadvantages mentioned above do not occur. In particular, it is the intention to propose a roller, whose mass distribution can be corrected at any time in a third balancing plane, in particular in the center of the roller, without the necessity of dismantling the roller trunnions.
This object is solved in accordance with the invention by a roller for thermally treating web-shaped media, comprising a roller body which is rotatable about its central longitudinal axis and peripheral bores in said roller body, introduced in axial parallel, for conveying a liquid heating medium, wherein other axially parallel balancing bores are formed in the roller body in addition to said peripheral bores for said heating medium, the balancing bores running from an end face of the roller body towards the center of the roller body.
Expedient embodiments are defined by the features of the sub-claims.
The advantages achieved by the invention are based on the fact that such a roller is provided, as early as during its manufacture, with at least three axially parallel balancing bores in the roller shell, which are expediently distributed uniformly over the circumference of the roller. These bores should reach as far as the vicinity of the center of the roller, but can easily also protrude beyond it, and begin at an end face of the roller body, thus being open outwards relative to the roller body.
The hollow spaces formed by these balancing bores alone change the weight distribution and can therefore have a balancing effect.
In many cases, however, these hollow spaces alone are not sufficient, such that in accordance with a preferred embodiment, balancing weights are then introduced into the center of the roller via these balancing bores. Using at least three compensating bores separated by ca. 120xc2x0 from each other, central imbalances and/or central deviations can be corrected in any direction.
In principle, it is also possible to introduce more than three balancing bores to accommodate the compensating weights; this can facilitate the balancing itself, but is more expensive to manufacture.
In the case of rollers comprising flanged trunnions, such as are often used today, it is possible to form these bores as an extension of the core bores for the threaded holes for screw-attaching the trunnions. These attaching screws for the flange trunnion can then be removed during the balancing procedure, since the radial load of the roller is limited to the weight of the roller, and the remaining attaching screws are sufficient for this purpose.
If a central deviation of the roller on a balancing machine is then established, said central deviation can be influenced by introducing balancing weights as far as the center of the roller via the threaded holes and the axially parallel balancing bores and the result can be immediately checked.
If the roller has been correctly balanced, then the attaching screws can be re-inserted and tightened, and a balanced roller is again available.
Balancing in this way can for example be necessary when an already balanced roller body is additionally provided with a coating after it has been assembled, and it has not been possible to apply said coating uniformly. Once the coating is complete, the central deviation can then be established and subsequently corrected.
It is further possible to correct a roller, which has been balanced while hot in order to establish its heated running characteristics, by introducing balancing weights via the additional bores, without having to dismantle the roller.